Interlock mechanism for sewing machines



'Nov. 30, 1943. H. GUNTHER INTERLOCK MECHANISMS FOR SEWING MACHINES Filed March 12, 1942 r e Wt WW $6 m O m w H Wifmss:

Q MM Elliot/am Patented Nov. 30, 1943 UNlTED STATES PATENT! QFFICE L'QTERLOCK MECHANISM FOR SEWING MACHINES Application March 12, 1942, Serial No. 434,338

'7 Claims.

This invention relates to sewing machines and more particularly to a safety interlock device therefor to prevent the operation of one mechanism of the machine while another mechanism thereof is operative.

Stated more specifically, the invention relates to article attaching machines having stitchforming mechanism controlled by acyclically operated stop-motion, a vertically movable workholder and article clamp and a thread-cutting mechanism.

In normal operation of uch machine, a workpiece is inserted beneath the work-holder, an article to be attached to the work-piece is placed in the article clamp, the stop-motion is manually tripped, by the operation of a suitable treadle to start the machine and the article is attached with a predetermined number of stitches, after which the stop-motion is automatically tripped to stop the machine. After the machine has come to rest, the operator, by actuation of a second treadle, lift the work-clamp and actuates the threadcutting mechanism to sever the thread.

It sometimes happens that, in an effort to obtain maximum production (such work being paid for on a piece-work basis), an operator will inadvertently depress the treadle which serves to raise the work-holder and article-clamp and actuate the thread-cutter, before the machine has been brought to rest or will trip the stop-motion into running position before the work-piece and article-clamp have been lowered and the threadcutter has been retracted'from its thread-cutting position. This usually results in damage to the machine as various parts thereof are accidentally brought into contact with each other.

To preclude this inadvertent or accidental operation of the machine, various forms of interlocking safety devices heretofore have been provided of which many have been complicated in construction and therefore costly to manufacture.

This invention has as its primary object to provide an improved and simplified interlocking safety device which will positively prevent the inadvertent or accidental operation of the machine, as above described, and which, though efficient in operation, is extremely simple in construction and inexpensive to manufacture.

This has been attained by the embodiment in an article attaching machine as disclosed in United States patent to Fifield, N0. 1,8783%, Sept. 20, 1932,.having therein all the mechanisms hereinbefore referred to, of a simplified interlocking device comprising only a single slotted and notched slide-bar, a cooperating stud and a single screw to guide the bar in its sliding-movements.

With the above and other objects in view, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawing of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby will be readily understood by those skilled in the art.

In the drawing, Fig. 1 is a left sideelevation of a button sewing machine embodying thepresent invention, showing the machine in stopped position but also showing, in dotted lines, the stop-motion shifted into running position and the interlocking slide-bar shifted to a position to prevent lifting of the work-clamp or'actuation of the thread-cutter.

Fig. 2 is a detail view of a portion of the interlocking slide-bar in the position it occupies when the machine is at rest and, in two positions, a portion of the thread-cutting mechanism.

Fig. 3 is a detail sectional view taken substantially on the line 3-3 of Fig. 1.

Referring more specifically to the drawing; the invention is disclosed as embodied in a Singer class 58 button sewing machine comprising a base I, standard 2 overhanging arm 3, bracketarm head 4 and horizontally disposed tubular work-supporting arm 5. Journaled lengthwise of the arm 3 is main shaft 6 which carries, at its rear end, tight and loose pulleys 1 and '8, respectively. A power-driven belt, not shown, driven from any suitable source, engages the pulleys l and 8 and rotates the shaft 6. At its forward end the shaft o is connected to reciprocate a laterally vibrating needle-bar (not shown) mounted in the head t and carryin an eye pointed needle (not shown) which cooperates with a loop-taker Q in the formation of article attaching stitches. The loop-taker is mounted in the work-supporting arm 5 and is actuated from the main shaft through mechanism designated generally as iii. Also mounted in the head 4 is the usual spring-depressed presser-bar, H which carries, at its lower end, a suitable presserfoot (not shown) and a conventional buttonclamp i2 having separable spring-pressed jaws l3 adapted to grip the shank of a button and hold it in stitch-receiving position upon a fabric'held by the presser-foot on a throat-plate l4 supported upon the work-supporting arm 5; The

presser-foot and button-clamp supportingbarll has fixed thereto the usual lifter-block l under the shoulder l6 of which extends the end ll of a manually operated presser-bar lifting lever l8, fulcrumed at I9, and having its rear end connected, by a chain 2|, to a suitable actuatin treadle, not shown.

Operation of the machine is controlled by a stop-motion mechanism comprising a stop-cam 22 secured upon the main shaft 6, with which cooperates the usual spring-pressed plunger 23, carried by a tilting stop-motion lever 24. The stop-motion lever carries the'usual belt-shipper 25 and includes a forwardly extending arm 26, which is connected, by a pull-rod 21, to a suitable starting treadle or knee-shift (not shown). The arm 26 of the stop-motion lever carries a pin 28 which is embraced by the forked arm 29 of a bellcrank lever 39 fulcrumed at 3| on the standard 2. The other arm 32 of the be l-crank lever carries a roller-stud 33 which, when the machine is in stopped position, rests in a notch 34 formed in the periphery of a stop-motion controlling cam 35. The cam 35 is secured upon a cross shaft 36 journaled in the standard 2 and rotated by a worm 31 and worm-wheel 38 from the main shaft 6.

When the stop-motion lever 24 is tilted to running position, by a down-pull on the starting rod 21, it is retained in such position by engagement of the hooked end 39 of a spring-pressed latch-arm 49, pivoted at 40 with an arm 4| which is rigidly mounted upon and constitutes a part of the stop-motion lever 24. By this movement of the stop-motion lever 24, the roller 33 is moved outwardly from the notch 34 in the stop-motion controlling disk or cam 35. There is mounted on the cam 35 a tripping-plate 42 having an inclined nose 43 adapted to strike the tail-pin 44 of a latch-lever 45 and deflect such tail-pin inwardly, thereby withdrawing the hooked end 39 of the latch-lever from the arm 4| and releasing the stop-motion lever 24 for movement to stopping position under the influence of its spring 45. The tripping-plate 42 is so timed upon the cam 35 that when its nose 43 engages the tail-pin 44 to release the stop-motionlever 24, the trailing end of the notch 34 has just passed the roller 33. Thus, although the stop-motion lever 24 has been released from the hold of the latch-lever 45, it cannot move to stopping position but is retained in running position by the roller 33 riding upon the circular portion of the periphery of the cam 35. If therefore, the operator pulls down on the rod 2| to start the machine and holds the rod down until the tripping-nose 43 passes the tail-pin 44, the latch-lever 45, in its recovery, will reengage the stop-motion lever 24 and hold it in running position for one revolution of the cam 35. At the end of the first revolution of the cam' 35, the latch-arm 45 will be tripped by the tripping nose 43 and the roller 33 will be permitted to ride upon the circular portion of the periphery of the cam 35 to retain the stop-motion lever 24 in running position during the second revolution of the cam 35 at the end of which the roller 33 will drop into the notch 34 and permit the stop-motion lever 24 to return to stopping position (shown in full lines in Fig. 1). The tripping plate 42 is secured to the cam disk 35 by means of two screws 41, 48. .The screw 47 passes through a slot 49 in the tripping-plate 42 to permit adjustment of the tripping-plate about the screw 48 as a center. Inasmuch as the screw 48 is located close to the axis of the shaft 36, the adjustment provides for,

the accurate timing of the tripping-nose 43 upon the cam 35.

The bobbin-thread pull-off and severing device, per se, is constructed substantially in accordance with the disclosure of the Fifield patent referred to. It comprises a reciprocatory bar 5| mounted on top of the work-supporting arm 5 and carrying at its forward end the vertically spaced cutter and pull-ofi blades 52 and 53, respectively. A stationary blade 54 is mounted on the under side of the throat-plate M in the path of the space between the blades 52 and 53. When the bar 5| carrying the blades 52 and 53 is projected from its inoperative position, shown in dotted lines in Fig. 2, to its operative position, shown in full lines, the pull-01f blade 53 engages the bobbin-thread and passes under the stationary blade 54, thereby forming a bight in the bobbin-thread and pulling a length thereof from the bobbin. The cutter-blade 52 passes over the stationary blade 54 and, being considerably shorter than the pull-off blade 53, does not engage and sever the bobbin-thread until after the pull-oif movement is practically completed. The bar 5| includes a hinged section 55 connected to one arm 56 of a bell-crank lever 56 fulcrumed on a stud 51 threaded into the standard 3. The other arm 56 of the bell-crank lever 56 is connected by the link 58 to the rearward end of the lever |8 lying behind the stop-motion controlling cam 35. The bobbin-thread pull-off and severing device is thus connected to the work-clamp opening mechanism and is manually operated by the same means which opens the work-clamp.

All of the above described mechanism is similar in construction and operation to the like parts shown and described more fully in said Fifield Patent No. 1,878,480.

The improved safety interlock device which precludes starting of the machine while the button-clamp is lifted, and lifting of the buttonclamp and actuation of the thread-cutter while the machine is in operation, comprises an inclined slide-bar 59, the upperend of whichis pivotally connected to the pin 28 carried by the stop-motion actuating arm 26. Adjacent its lowerend the slide-bar is formed with a guideslot 68 through which extends a shoulder screw 6| threaded into the stud 57 on which the bellcrank lever 56 is fulcrumed. The shoulder screw 6| and slot 60 serve to guide the slide-bar 59 as it is moved endwise by swinging movement of the stop-motion arm 26. Also adjacent its lower end the slide-bar 59 is formed with a notch 62 into which, at certain times, moves a roller-stud 63 carried by the arm 56 of the bell-crank lever 56, as shown in Fig. 2.

. When the machine is at rest, with the stopmotion and slide-bar 59 in the positions shown in full lines in Fig. 1 the operator may, by actuating a suitable treadle, pull downwardly on the chain 2|, thereby rocking the presser-foot and button-clamp lifting-lever l8 counterclockwise and lifting the button-clamp carrying bar II. This movement of the lever |8 alsoshifts'the link 53 endwise downwardly thereby turning the bell-crank lever 56 clockwise aboutits fulcrum, and advancing the link 55 and thread-cutter. actuating bar 5| to sever the thread. ,During this turning movement ofthe bell-crank lever 56 the stud 63 enters the notch 62 in the slidebar 59 as shown in full lines in Fig. 2, thus look ing that bar against endwise movement. With the bar 59 locked against movement the stopmotion lever 24 may not be swung to the dotted line position shown in Fig. 1 to start the machine. Thus starting of the machine is prevented when the button-clamp is lifted and the threadcutter is advanced.

When the stop-motion is in the position shown in dotted lines in Fig. l the machine is running. In that position of the stop-motion the slide-bar 59 is shifted downwardly to the position shown in dotted lines in Fig. 1 so that the edge 5% thereof lies adjacent the roller-stud 63 and obstructs movement thereof. With the parts in this position the bell-crank lever 55 may not be turned clockwise, as seen in Fig. 1, and therefore the button-clamp may not be raised and the thread-cutter may not be advanced.

From the foregoing it will be perceived that the slide-bar 59 with its notch 62, in cooperation with the stud 63 on the bell-crank lever 56, afford a simple interlock whereby operation of the clamp-lifter and thread-cutter is precluded during running of the machine and likewise starting of the machine is prevented when the button-clamp is lifted and the thread-cutter is advanced.

Having thus set forth the nature of the invention what I claim herein is:

1. In a sewing machine, the combination with a rotary main shaft, a stop-motion shiftable back and forth from one position to another alternately to effect starting and stopping of said main shaft, a work-holder, and means for shifting said work-holder from an operative position to an inoperative position, of an interlock device to prevent shifting of said stop-motion to start rotation of said shaft while said work-holder is in its inoperative position, comprising an upwardly inclined slide-bar connected at its upper end to said stop-motion to be shifted thereby, means for guiding the lower end of said slidebar for substantially straight line movement, and an abutment member shiftable into the path of movement of said slide-bar by the movement of said work-holder shifting means.

2. In a sewing machine, the combination with a rotary main shaft, a stop-motion shiftable back and forth from one position to another alternately to effect starting and stopping of said main shaft, a work-holder, and means including a lever for shifting said work-holder from an operative position to an inoperative position, of an interlock device to prevent shifting of said stop-motion to start rotation of said shaft while said work-holder is in its inoperative position, comprising a notched slide-bar connected to said stop-motion to be shifted endwise thereby and an abutment member shiftable into the notch in said slide-bar by the movement of said workholder shifting lever.

3. In a sewing machine, the combination with a rotary main shaft, a stop-motion shiftable back and forth from one position to another alternately to effect starting and stopping of said main shaft, a work-holder, and means for lifting said workholder from an operative position to an inoperative position, of an interlock device to prevent shifting of said stop-motion to start rotation of said shaft while said work-holder is in its inoperative position and to prevent lifting of said work-holder while the stop-motion is in machinedriving position, comprising a slide-bar connected at one end to said stop-motion to be shifted endwise thereby, guide means engaging said slidebar adjacent its other end to guide the bar in its sliding movements, a lever operatively connected with said work-holder shifting means and movable thereby, and an abutment member carried by said lever and shiftable into the path of movement of said slide-bar by the movement of said work-holder shifting means, said slide-bar being arranged in the path of movement of said abutment when said stop-motion is in machine stopping position and thereby preventing lifting of said work-holder.

4. In a sewing machine, the combination with a rotary main shaft, a stop-motion shiftable back and forth from one position to another alternately to effect starting and stopping of said main shaft, a thread-cutter, and means for shifting said thread-cutter from an inoperative position to an operative position, said means including a manually actuated lever, a slide-bar connected with said thread-cutter, a bell-crank lever having one arm connected to said slide-bar and a link connecting said manually actuated lever with the other arm of said bell-crank lever, of an interlock device to prevent shifting of said stop-motion to start rotation of said shaft while said threadcutter is in its operative position, comprising a notched slide-bar connected to said stop-motion to be shifted thereby and an abutment member carried by said bell-crank lever and shiftable into the notch in said slide-bar by the movement of said bell-crank lever to actuate the thread-cutter to sever th thread.

5. In a sewing machine, the combination with a rotary main shaft, a stop-motion shiftable back and forth from one position to another alternately to effect starting and stopping of said main shaft, a thread-cutter, and means for shifting said thread-cutter from an inoperative position to an operative position, said means including a manually actuable lever, a slide-bar connected with said thread-cutter, a bell-crank lever having one arm connected to said slide-bar and a link connecting said manually actuable lever with the other arm of said bell-crank lever, of an interlock device to prevent shifting of said threadcutter into thread-cutting position during running of the machine, comprising a stud carried by said bell-crank lever and a second slide-bar connected directly to said stop-motion to be shifted thereby to a position where it lies in the path of said stud and prevents movement thereof when said stop-motion is shifted to machine starting position.

6. The combination set forth in claim 5 in which the slide-bar, which engages the stud on the thread-cutter-shifting bell-crank lever to prevent actuation of the thread-cutter when the stop motion is in machine starting position, has a portion formed with a slot adjacent the fulcrum of said bell-crank lever, and a guide-screw extends through said slot and is threaded into and coaxial with the fulcrum of said bell-crank lever to guide one end of said slide-bar.

7. The combination set forth in claim 5 in which the second slide-bar is formed with a notch which lies adjacent to said stud when the stop-motion is in machine stopping position and into which the stud on said bell-crank lever moves when the thread cutter is shifted to thread-cutting position, thereby to prevent endwise movement of said slide-bar and consequently to prevent the stop-motion from being shifted into machine starting position.

I-IERMANN GUNTI-IER. 

